1. Field of the Invention
The present invention relates to a demultiplexer, and more particularly, to a demultiplexing apparatus and method, which simultaneously demultiplexes a plurality of transport streams (TSs) having different structures so that TSs can be stored in a storage medium such as a hard disc drive (HDD), or TSs can be easily transmitted through an IEEE1394 or peripheral component interconnect (PCI).
2. Description of the Related Art
To transmit encoded audio, video and other supplement data (program selection information, program guide information, scramble information, etc.) in digital satellite broadcasting or ground wave broadcasting, data should be packetized, multiplexed into a program stream (PS) or a transport stream (TS), and then transmitted.
The TS is used mainly for the case where bit streams are to be transmitted through a medium which has a high possibility of errors. Within the TS, the size of a packet is fixed so that parity information can be added for error correction.
In the case when using moving picture experts group-2 (MPEG-2), the size of a TS packet is fixed at 188 bytes, and each packet is formed of a 4-byte header and a 184-byte payload.
Meanwhile, in the case when using distributed sample scramble (DSS), the size of a TS packet is fixed at 130 bytes, and each packet is formed of a 2-byte prefix (header) field and a 128-byte transmission block (payload).
The header of each packet contains packet identification (PID, or SCID in DSS's case), which indicates what information is loaded in the payload, and scramble information as well. The payload loads video, audio, and other tables, wherein the tables include a program map table (PMT) and a program association table (PAT), which is formed by the program map tables.
The DSS TS demultiplexer has been implemented in various ways by multiple companies, and the models can be roughly divided into two types: a type having an embedded microprocessor for demultiplexing, and the other type without the microprocessor.
Meanwhile, the MPEG-2 TS demultiplexer of C-cube Co., which is now widely used, has an embedded Reduced Instruction Set Computer (RISC) engine. This demultiplexer cannot process a DSS TS, but can process an MPEG-2 TS.
There are demultiplexers sold by some companies in addition to C-cube's demultiplexer. However, these demultiplexers cannot process a DSS TS, or even when a DSS TS can be processed, these demultiplexers cannot simultaneously process a DSS TS and MPEG-2 TS due to limitations of having only one input for receiving a TS. Also, in a TS transmitted through PCI or IEEE1394, a predetermined packet cannot be replaced with a new packet, and a path for processing TS data cannot be changed in a state where the TS input is fixed.